Control valve assembly for a pneumatically operated fastener device

ABSTRACT

Within the valve piston of a control valve assembly for a pneumatically operated fastener device, an auxiliary valve member is slidably mounted on the valve stem which valve member is designed as a differential piston, the middle annular area of which communicates with the open air whereas the upper smaller face communicates with a chamber which, in its turn, communicates with the valve housing space beneath the valve piston. Compressed air is supplied to this chamber when the valve piston moves to open position and the valve piston is returned to closed position upon completion of the working stroke of the tool, whereby a higher sequence of working strokes is achieved.

Jurgen Korth [72] lnventor n ".w "u" S flun m m m m mmm k w T 08 y 03y r. VBL m 567% 666 999 W 111 .n 5 6 n n m 67.2 E 620 w 003 a 822 m n 333 P 7 Birkenweg 3001, Berenbostel, Germany Appl. No. 761,027 [22] F iled Sept. 20, 1968 [45] Patented Jan. 12, 1971 Attorney-Hibbn, Noyes & Bicknell [54] CONTROL VALVE ASSEMBLY FOR A ABSTRACT: within the valve piston of a control valve aslly operated fastener device, an aux- PNEUMATICALLY OPERATED F ASTENER DEVICE sembly for a pneumatica iliary valve member is slidably mounted on the valve stem which valve member is des igned as a differential piston, the ch communicates with the open air l37/625.6 F16k 11/07 middle annular area of whi whereas the upper smaller face communicates with a chamber 137/6255, which, in its turn, communicates with the valve housin beneath the valve piston. Com

[51] Int. [50] Field g space pressed air is supplied to this References Cited UNITED STATES PATENTS 2,964,057 12/1960 Dyson.................;........

chamber when the valve piston moves to open position and the valve piston is returned to closed position upon completion of the working stroke of the tool, whereby a higher sequence of working strokes is achieved.

PATENTED JAN] 219m SHEET 1' OF 3 JURGEM K mimm m SHEVET 2 -UF' 3 conrnor. VALVE ASSEMBLY Fort A PNEUMATICALLY OPERATED FASTENER DEVICE The present invention refers'to a control valve assembly for a pneumatically operated fastener device and, in particular,

- for a compressed-air-driven hand-operated apparatus to drive valve piston sliding on a valve stem and connecting the working cylinder during operation with a source of compressed air and, in its initial position, with the open air. For the purpose'of initiating a working stroke, the valve stem must be raised manually which requires acertain period of time as also a certain physical forceexercised by the finger of the operator. The sequence of working strokes effected by meansv of this prior art control-valve assembly is limited to a relative small range.

It is an important object of the present invention to provide a control-valve-assembly for a pneumatic device which enables a high sequenceof working strokes and thereby an essential increase of efficiency of the device.

A further object of the invention is to provide a pneumatic device which operates more smoothly and with less vibration than was the case hitherto,,so as to enable. the pneumatic hand-operated device to be easier to handle.

According. to the invention, there is slidably mounted, on

the valve stern of a stepped-piston type control valve piston,

an auxiliaryvalve member designed as a differential piston and enclosed by said control-valve piston. The middle annular area of this differential piston communicates with the open air, whereas the upper smaller face encloses, together with the I valve piston, a chamber which, via a throttle passage, communicates, in its turn, withacharnber of the valve'housing provided beneaththe valve piston. v

According to another feature of the invention an auxiliary passage is provided parallel to an axial bore of the valve stem. Said auxiliary passage in the lower end position of the auxiliary valve member, connects the chamber between its upper face and the inner wall of the valve piston with a compressed air supply passage permanently communicating with a source of compressed air. By this arrangement the valve piston designed as a differentialpiston is moved to its initial position in which the working cylinder is closed against the compressed air supply passage and 'is'vented'withoutany necessity of a downward displacement of the stem of the valve piston for this purpose. As the valve piston has been returned to its initial position in which the supply of. compressed air to the working cylinder is closedand as the release valve stem has not been moved for this purpose, thedevice is again ready for operation as soon as the working stroke has been completed. As this restricts the number of movements of the release valve stem and as the intervals between the individual working strokes are smaller, this arrangement ensures a substantialincrease of the sequence of strokes and a smooth working of the handoperated device.

' FIG. 2 is a longitudinal section of the control valve assembly when the device is in its initial or normal position; FIG. 3 is the longitudinal section of FIG. 2 during the working stroke of the piston, and

FIG. 4 is the longitudinal section in the position after completion of the working stroke when the control valve is in the position ready for operation.

With reference to FIG. l, the compressed air actuatedportable device to drive in staples is provided with a hollow housing body 1 designed to form a handle. In the rear portion of this housing body 1 is arranged a conventional connection 2 for a suitable supply of air under pressure. In the hollow handle, there is provided a compressed air supply passage 3 permanently connected to the supply of air under pressure. Said compressed air supply passage 3 is extended to form a storage chamber and, via a control valve 4, communicates with a passage 5 leading to a working cylinder 6'located .in the front part of the housing body 1. In the working cylinder 6 a piston 7 is slidably mounted which in a conventional manner operates a staple driver 8. This driver drives into a workpiece staples from the magazine 9 located in the bottom part of the housing body 1.

As is illustrated in FIGS. 2 to 4, the-control valve 4 is provided with a valve housing 10 screwed into a threaded bore-of the housing body 1 and an upper housing part 21 held bysaid valve housing 10. The control valve 4 is of the stepped-pistont-ype and possesses an upper face ll permanently exposed to the action of the compressed air in the compressed air supply passage 3. The control valve 4 is slidably mounted on a release-valve stem 12 the lower end 13 of whichforms a pin and rests on the finger-operated valve trigger lever l4 pivotedr said shoulder being designed to form a valve seat. The sealing In a further embodiment of theinvention the chamber between the upper face of the auxiliary piston and the inner wall of the control valvecommunicates with the valve housing space beneath the latter via a narrow passage the aerodynamic resistance of which is dimensioned in such a way that a pressure sufficient to raise the control valve into its initial position cannot be produced in said valve housing space until the' illustration is shown as applied to a'portable pneumatic sta-- pler. In the drawings: v 7

FIG. 1 is aside elevation and a partiallongitudinal section of a compressed air-driven hand-operated stapler with the control valve assembly embodying this invention;

passage, which is provided with a sealing element 23. The

spacing of said release-valve stem I2 from said upper end wall 24 is in the order of some one sixty-fourth inches and conforms to the stroke of thelower end 13 of therelease-valve stem 12 operated by the trigger lever 14.

At the joint of the valve housing 10 and'itsupper part 21 I there is provided a port25 extending into a vent passage26 of the housing body 1.

The lower portion 27 of' the stepped-piston-type control valve 4 has a surface which consists of two stepped -;co neshaped shells 28 and 29. The lower portion 27 is provided with a stepped axial recess 30 which encloses a steppedpiston-type auxiliary piston'3l. In the same manner as the control piston 4, this auxiliary piston 31 is slidably mounted on thereleasevalve stem 12 and, in its upper portion, is sealed against. said stem 12 by a sealing ring 32. The lower end of the auxiliary piston 31 has an increased diameter and, by a sealing 'ring13'3,

is sealed against the lower portion 27 of the control valve 4 which, in its turn, is sealed against the valve housing 10 by a sealing ring 34. The valve housing space 35 beneath the control valve 4 is in perrnanentlyopen communication with the axial bore 22 of the release-valve stem 12 by means of a radial bore 36 in the stem 12 and, over and above this, communicates, via a clearance 37 in a bottom. plate 38 closingthe valve housing space 35 at the lower end as also via an elongated slot 39 in the lower end 13 of the release-valvestem 12, with the open air when the release-valve stem 12 is in'itsupper end position as shown in FIGS/3 and4 in which position-the shoulder 40 of the release-valve stem 12 is raised from the bottom plate 38. In the initial or normal position shown in FIG. 2, the clearance 37 of the bottom plate 38 is sealed by the shoulder 40 so that the valve housing space 35 is closed against the open air.

A space 41 enclosed between the upper portion 21 of the valve housing 10 on the one hand and the cone-shaped shells 28, 29 of the lower portion 27 of the control valve 4 on the other communicates, via a passage 42 provided at the joint of the two cone-shaped areas 28 and 29, with the lower part of the recess 30 of the control valve 4 which lower part is increased in diameter. Furthermore, the inner wall of the upper part 16 of the control valve 4 on the one hand and the upper annular area of the auxiliary piston 31 on the other jointly form a chamber 43, which, via a narrow or restricted passage 44, communicates with the lower valve-housing space 35. An auxiliary passage 45 is arranged parallel to the axial bore 22 in the release-valve stem 12. In the position of the release-valve stem 12 shown in FIGS. 3 and 4 this auxiliary passage 45 communicates at its lower end with chamber 43 and atits upper end with the compressed air supply passage 3.

The operation of this control-valve assembly is the followmg:

In the normal or initial position of the control-valve assembly as shown in FIG. 2, the compressed air supply passage 3 is in open communication with the valve housing space 35 beneath the control valve 4 or the lower portion 27 of same, respectively, via the axial bore 22 and the radial bore 36 of the release-valve stem 12. As the annular area of the bottom part of the control valve 4 or the lower portion 27 of same, respectively, and the bottom face of the auxiliary piston 31 enclosed by said annular area together possess a larger operative area than the upper face 11 of the control valve 4 permanently exposed to the action of the compressed air from the compressed air supply passage 3, the control valve 4 is retained in its closed position by the resulting pressure difference. Thus, the passage leading to working cylinder 6 is sealed against compressed air supply passage 3 and, via space 41 of the upper portion 21 of the valve housing and the port 25 of same, is in open communication with the vent passage 26. The lower valve housing space 35 is sealed against the clearance 37 and the elongated slot 39 of the pin-type lower end 13 of the release-valve stem 12 and, consequently, against the open air by the shoulder 40 at the lower end of the release-valve stem 12. The lower end of the auxiliary passage 45 is closed by the raised auxiliary piston 31 and its sealing ring 32 so that no compressed air reaches chamber 43.

In order to open control valve 4, valve trigger lever 14 is turned upwards so that release-valve stem 12 reaches the position shown in FIG. 3 in which position its upper end comes to rest against the sealing element 23 of the upper end wall 24 of compressed air supply passage 3 so that the axial bore 22 is sealed against the compressed air. At the same time, the elongated slot 39 of the lower end 13 of release-valve stem 12 is opened by raising shoulder 40 of said stem 12 so that the lower valve-housing space 35 is vented. This permits the compressed air in compressed air supply passage 3 to push control valve 4 downwards and to open valve seat 19. The compressed air from compressed air supply passage 3 now flows into passage 5 leading to working cylinder 6 and acts upon piston 7 which then makes its working stroke.

The downward movement of control valve 4 opens the lower end of auxiliary passage 45 through which the compressed air from compressed air supply passage 3 reaches chamber 43. From here, the air flows, through narrow passage 44, into the lower'valve housing space 35. The aerodynamic resistance of this narrow passage 44 is dimensioned in such a manner that a pressure sufiicient to raise control valve 4 cannot develop in the lower valve-housing space 35 until piston 7 in working cylinder 6 has completed its working stroke. It follows that control valve 4 is moved upwards in its closed position as shown in FIG. 4 by the air pressure built up in the lower valve-housing space 35 while valve trigger lever 14 is still turned upwards. The auxiliary piston 31 still remains in its lower end position because the compressed air in chamber 43 acts on its upper face whereas its bottom side is vented via clearance 37 of the elastic bottom plate 38 opened by the raised shoulder 40 as well as via the elongated slot 39 of the pin-type lower end 13 of release-valve stem 12. As seen in FIG. 4, an axial end recess 47 is provided in the auxiliary piston 31 which receives the raised shoulder 40 while the annular lower end of the auxiliary piston 31 is held lower sealed relation against the elastic bottom plate 38. When the control valve 4 moves upwardly relative to the auxiliary piston 31, an annular chamber 46 over the stepped upper part of the auxiliary piston 31 is formed. Via passage 42, this annular chamber 46 communicates with space 41 in the upper part 21 of valve housing 10 which space is vented via port 25 and vent passage 26. Apart from this, passage 5 leading to working cylinder 6 is in open communication with vent passage 26 when control valve 4 is in closed position as shown in FIG. 4.

In order to initiate a working stroke, it is only necessary that valve trigger lever 14 is relieved from the pressure of the finger of the operator for a very short period. This causes the release-valve stem 12 to be moved downs downwards to the position shown in FIG. 2 while the position of control valve 4 remains unchanged. In this position, the clearance 37 of elastic bottom plate 38 as well as the elongated slot 39 of the pin-type lower end 13 of release-valve stem 12 are closed by the shoulder 40 of release-valve stem 12. Compressed air from compressed air supply passage 3 now flows into the portion of the lower valve-housing space 35 enclosed by the recess 47 through axial bore 22 as well as through the radial bore 36 and raises auxiliary piston 31 from its lower end position shown in FIG. 4 into the upper position shown in FIG. 2 in which the auxiliary passage 45 is sealed against compressed air supply passage 3. The device is then, again, ready for operation and makes its working stroke as soon as valve trigger lever 14 is pivoted upwards, because control valve 4 then reaches its opened position as shown in FIG. 3.

The structure of the control valve assembly according to the present invention enables an essential increase of the sequence of working strokes, as the compressed air flowing through the narrow passage 44 moves the control valve into its sealing position as soon as the working stroke of piston 7 is completed.

The present invention is of considerable advantage for pneumatic equipment of all kinds, and in particular for portable pneumatic percussion devices presupposing a rapid series of working strokes and, on account of the small actuating manual force required, allows of a considerable increase of the performance of such devices. This is of particular importance where the percussion device is concerned for driving in staples, nails and other fasteners, so widely used in am mass production. The invention is also of importance for pliers and packing devices for stapling the lids of cardboard boxes.

Iclaim:

1. A control valve assembly for a pneumatically operated fastener driving too] having a body containing a compressed air supply chamber, a working cylinder with a driving piston therein, a main air supply passage for connecting said air supply chamber with said working cylinder in operating position of the control valve assembly, and a main vent passage for venting said working cylinder in normal position of the control valve assembly;

said control valve assembly comprising in combination:

a valve housing mounted in the tool body and having openings communicating with said main air supply and main vent passages;

a valve stem shiftably disposed in said housing with one end extending into said air supply chamber and its opposite end projecting from said housing for engagement with a manually operated actuating member, said valve stem having axial bore extending from said one end and communication with a space in said housing adjacent said opposite end of said valve stem;

seal means cooperating between said valve stem and said housing for sealing said housing space in normal position of the control valve assembly and for venting said housing space in operating position of saidcontrol valve assembly;

a differential piston-type control .valve slidably mounted on said valve stem within said housing, said control valve having an internal axial recess and also having an intermediate portion spaced from said housing and defining therewith a vent space within said housing permanently communicating with said main vent passage, said control valve being movable between an open position in which said air supply chamber is in communication with said main air supply passage but said main vent passage is sealed off and a closed position in which said main air supply passage is closed relative to said air supply chamber but is in communication through said vent space with said main vent passage;

an auxiliary differential piston slidably mounted on said valve stem within said recess of said control valve, said auxiliary piston having'a portion axially spaced from the inner end of said recess to provide an air pressure chamber therebetween;

vent passage means in said control valve connecting said recess with said vent space;

auxiliary air passage means for supplying compressed air to said air pressure chamber in operating position of the control valve assembly; and

throttle passage means in said control valve communicating between said air pressure chamber and said housing space for effecting movement of said control valve from open position to close position while the control valve assembly is still in operating position; said throttle passage means being of restricted dimensions such that said control valve is not moved 'to cldsed position until after the working piston has completed its working stroke.

2. The control valve assembly of claim I further characterized in that said internal axial recess in said control valve comprises a stepped recess surrounding said valve stem and including a smaller diameter recess portion and a larger diameter recess portion, said auxiliary piston has a stepped configuration including a smaller diameter piston portion disposed in said smaller diameter recess portion of said control valve and a larger diameter piston disposed in said larger diameter recess portion of said control valve. said smaller diameter piston portion being axially spaced from the inner end of said smaller diameter recess portion to provide said air pressure chamber therebetween, and said vent passage means connects said larger diameter recess portion of said control valve with said vent space.

3. The control valve assembly of claim 1 wherein said aux iliary air passage means comprises an auxiliary passage in said valve stem having an inlet end in permanent communication with said air supply chamber and an outlet end movable into communication with said air pressure chamber when the control valve assembly is in operative position.

4. The control valve assembly of claim 1 wherein said larger diameter piston portion of said auxiliary piston is provided with an axial recess adapted to enclose said seal means when the control valve assembly is in operative position. 

1. A control valve assembly for a pneumatically operated fastener driving tool having a body containing a compressed air supply chamber, a working cylinder with a driving piston therein, a main air supply passage for connecting said air supply chamber with said working cylinder in operating position of the control valve assembly, and a main vent passage for venting said working cylinder in normal position of the control valve assembly; said control valve assembly comprising in combination: a valve housing mounted in the tool body and having openings communicating with said main air supply and main vent passages; a valve stem shiftably disposed in said housing with one end extending into said air supply chamber and its opposite end projecting from said housing for engagement with a manually operated actuating member, said valve stem having axial bore extending from said one end and communication with a space in said housing adjacent said opposite end of said valve stem; seal means cooperating between said valve stem and said housing for sealing said housing space in normal position of the control valve assembly and for venting said housing space in operating position of said control valve assembly; a differential piston-type control valve slidably mounted on said valve stem within said housing, said control valve having an internal axial recess and also having an intermediate portion spaced from said housing and defining therewith a vent space within said housing permanently communicating with said main vent passage, said control valve being movable between an open position in which said air supply chamber is in communication with said main air supply passage but said main vent passage is sealed off and a closed position in which said main air supply passage is closed relative to said air supply chamber but is in communication through said vent space with said main vent passage; an auxiliary differential piston slidably mounted on said valve stem within said recess of said control valve, said auxiliary piston having a portion axially spaced from the inner end of said recess to provide an air pressure chamber therebetween; vent passage means in said control valve connecting said recess with said vent space; auxiliary air passage means for supplying compressed air to said air pressure chamber in operating position of the control valve assembly; and throttle passage means in said control valve communicating between said air pressure chamber and said housing space for effecting movement of said control valve from open position to close position while the control valve assembly is still in operating position, said throttle passage means being of restricted dimensions such that said control valve is not moved to closed position until after the working piston has completed its working stroke.
 2. The control valve assembly of claim 1 further characterized in that saId internal axial recess in said control valve comprises a stepped recess surrounding said valve stem and including a smaller diameter recess portion and a larger diameter recess portion, said auxiliary piston has a stepped configuration including a smaller diameter piston portion disposed in said smaller diameter recess portion of said control valve and a larger diameter piston disposed in said larger diameter recess portion of said control valve, said smaller diameter piston portion being axially spaced from the inner end of said smaller diameter recess portion to provide said air pressure chamber therebetween, and said vent passage means connects said larger diameter recess portion of said control valve with said vent space.
 3. The control valve assembly of claim 1 wherein said auxiliary air passage means comprises an auxiliary passage in said valve stem having an inlet end in permanent communication with said air supply chamber and an outlet end movable into communication with said air pressure chamber when the control valve assembly is in operative position.
 4. The control valve assembly of claim 1 wherein said larger diameter piston portion of said auxiliary piston is provided with an axial recess adapted to enclose said seal means when the control valve assembly is in operative position. 